Black Box G.703 NTU w/V35, Manual

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G.703 NTU W/V35
13
4.9 Local loop diagnostics
The MT331A offers V.54 loop diagnostics. Use these diagnostics to test the NTU
and any communication links. This test can be activated via DIP switches or via
signals on the MT331A serial port interface.
4.9.18 O
PERATING LOCAL LOOPBACK
(LL)
The Local Loopback (LL) test checks the operation of the local MT331A, and is
performed separately on each unit. Any data sent to the local MT331A in this test
mode will be echoed (returned) to the user device (i.e., characters typed on the
keyboard of a terminal will appear on the terminal screen)
Figure 6. Local Loopback for a network termination application
To perform a LL test, follow these steps:
1. Activate LL. This may be done in one of two ways:
— Place the DIP switch SW1-2 to the “ON” position.
— Activate the “LL” signal on the DTE. If you are not sure which lead is
the “LL” signal, please refer to appendix B. “Interface pin assignment”
on page 15.
2. Verify that the data terminal equipment is operating properly and can be
used for a test.
Serial
Device
Serial
Device
MT311A
Receive
Recover
Clocking
Internal
Clocking
Cable
Span
G.703 NTU
MT331A
G.703 NTU
MT331A
Clock/
Data
Clock/
Data
Clock/
Data
Data
Data
MT311A